Current projects

North King County/South Snohomish County projects

North Creek Interceptor – The county will complete construction to repair and replace a 2-mile pipeline that has been serving the Bothell area since 1970. The new pipeline will increase system reliability and accommodate population growth in this portion of the service area.

Seattle projects

Chelan combined sewer overflow control – This project will serve West Seattle neighborhoods. It will add capacity to store 4.3 million gallons of stormwater and sewage by constructing a new below-ground storage facility. When the project is complete in 2023, it will prevent a significant amount of harmful sewage overflow from entering our waterways.

Denny Way Regulator Station upgrade – In early 2017, King County is starting construction work at the Denny Way Regulator Station in Myrtle Edwards Park on Elliott Bay. The project will update equipment and add a sampling room to the facility. Construction activity is expected to last one year.

Georgetown Wet Weather Treatment Station – King County will continue design on a new combined sewer overflow (CSO) facility in Seattle’s Georgetown neighborhood that will treat up to 70 million gallons of stormwater and sewage that currently flows directly into the Duwamish River during heavy rains.

Rainier Valley wet weather storage – King County is beginning construction of a new combined sewer overflow (CSO) underground tank and sewer pipelines in Seattle’s North Beacon Hill and Columbia City neighborhoods, which will control overflows of stormwater and sewage into the Duwamish River during heavy rains.

Sediment management program – This program enables King County to address sediment contamination near CSO locations in Puget Sound. The county is continuing its efforts to remove historic CSO contamination and restore habitat at locations in Elliott Bay and the Waterway.

Ship Canal water quality – Seattle Public Utilities and King County are working together to build an underground storage tunnel. During storms, this tunnel will hold polluted water from Ballard, Fremont, Wallingford, and north Queen Anne, preventing it from overflowing into the Lake Washington Ship Canal.

South Magnolia combined sewer overflow control – Work on King County's Magnolia Wet Weather Storage Facility at Smith Cove was completed in early 2016! The project's 1.5-million-gallon underground tank can store excess flows of stormwater and sewage from heavy rains to reduce untreated overflows to Puget Sound.

University green stormwater infrastructure - King County is beginning a green stormwater infrastructure project in north Seattle. This project will install facilities to help control a combined sewer overflow in Portage Bay. In 2017-18, the project team will study soil, groundwater, surface water flow, and street conditions in the project area to identify the best locations for facilities to be installed.

West Duwamish CSO control – King County is exploring several alternatives for reducing combined sewer overflows (CSOs) at the Terminal 115 and West Michigan outfalls. There are several options: a 100% “green” solution that could include roadside rain gardens and/or permeable pavement that lets water soak through it, a traditional “gray” infrastructure solution such as an underground storage tank or pipe, or a mix of green and gray.

West Point Treatment Plant improvements – King County plans a number of improvements at the West Point Treatment Plant. Projects include upgrading and replacing aging equipment to ensure reliable operation and continued compliance with permit conditions.

East King County projects

Coal Creek sewer upgrade – King County is planning to upgrade a regional sewer line that serves Bellevue and Newscastle. The existing pipeline was built between 1966 and 1991, and is nearing its maximum capacity. When complete, the new sewer will provide safe and reliable service for another 50 years or more.

Lake Hills and NW Lake Sammamish sewer upgrade – King County is beginning design on a project to upgrade 21,000 feet of aging pipeline in Redmond that has been in service for as long as 60 years. The new pipeline will increase system reliability and accommodate population growth.

King County is designing a new vehicle maintenance and staging facility for transporting Loop biosolids. The new facility, expected to be open in winter 2018, will be located in North Bend (exit 34 off I-90) on County-owned land.

North Mercer Island and Enatai sewer upgrade – King County will continue project planning and design to replace sewer pipelines that have served neighborhoods in North Mercer Island, southwest Bellevue, and the town of Beaux Arts Village since 1970. The new pipeline is being designed to serve these communities for the next 60 years.

Sunset and Heathfield pump stations upgrades – King County plans to upgrade two pump stations in Bellevue as well as connecting sewer pipelines. The project also entails upgrading the Eastgate Trunk structure near I-90, which enables wastewater from these pump stations to get to King County’s South Treatment Plant in Renton.

South King County projects

Kent-Auburn conveyance system improvements (Phase B) – In 2016, King County will invest $3.1 million to expand the capacity of the wastewater conveyance system in the south portion of its service area. Construction will include installing new sewer lines and replacing aging pipes in Pacific, Algona, and Auburn. Work will also include modifications to piping at the Pacific Pump Station in Pacific.

South Treatment Plant improvements – King County has a number of projects at the South Treatment Plant in Renton to replace or upgrade critical treatment plant equipment including pumps motors, and drives, which will improve system reliability, reduce maintenance costs and increase energy efficiency.

Regionwide projects

Conveyance system improvements – the utility is engaging in activities that guide the planning, design, and construction of new pipeline improvements and expansions within the utility’s 420-square-mile service area.

Lower Duwamish Waterway Superfund – King County continues to work on Superfund activities to address historically contaminated sediments in the waterway. King County will also maintain its involvement in the Lower Duwamish Waterway Group in 2016, which is currently working with EPA and the state Department of Ecology to identify a Superfund cleanup strategy.

Conveyance system H2S corrosion rehabilitation – King County will repair and replace sewer pipelines throughout its service area that are deteriorating or damaged as a result of corrosion caused by hydrogen sulfide gas, which commonly occurs in sewage. A current project is the Eastgate Sewer Pipeline Lining Project.

WTD Resiliency and Recovery Program – King County plans to assess and retrofit sewer infrastructure and buildings in preparation for potential seismic events. The program goal is to protect public safety by avoiding or minimizing critical system damage that could occur during a natural disaster.